"Pay no attention to what I'm doing here," says Mike Stone, in his best Wizard of Oz voice. "Just look out the window and keep pedaling."

I keep pedaling, breaking into a sweat but going nowhere, as my bike is mounted on what's called a trainer in the bike-fitting studio in the back of Princeton Sports in Columbia. And then I do look away from the window and see that "Stoney," as he's known, has set up some kind of laser on the windowsill and is projecting a red line along my left leg. The line is showing that my knee gravitates to the side as I pedal. To fix this, Stone will later insert a thin shim into my bike sole.

Welcome to the world of customized bike fits, a place I never thought middle-aged me would end up. Four years ago, I hired a personal trainer who convinced me that I could do a triathlon even though no one had ever accused me of being athletic. And I soon became part of some statistics: the growing number of triathletes and, in particular, the growing numbers of women who have latched onto the sport with the same enthusiasm they once reserved for PTA meetings. (Membership in USA Triathlon has more than quadrupled, rising from about 130,000 in 2000 to 550,446 in 2012, and women have grown from 27 percent of the membership to 37 percent.)

I rode my heavy hybrid bike in races, telling myself that if I stayed with the sport for four years, I might pony up for a better bike. This spring, I bought a triathlon bike that was such a fine piece of machinery that it terrified me. I called it Flavia because it seemed young and daring, like the character in the Alan Bradley novels.

The salespeople at Princeton Sports who sold me the bike also suggested I get it fit. "Go to Mike Stone," said, noting that he had just come back from some sort of intensive training in California.

And so I stumbled my way into another statistic: the growing number of people obsessed with the comfort and power of a good fit.

If the program fits

"If you walked into a bike shop 10 years ago," says Stone, "and asked what the best use for $500 was, you would have been told a new wheel set."

Now it's all about the fit.

Alan Davis, who, along with his brother, owns Princeton Sports, first sent Mike and other employees to Specialized Bicycle Components University in California in 2008. He said he saw the rise in interest in cycling and triathlon, and he wanted to be the first bike shop in the area to offer detailed fitting services.

Run by the American bike company Specialized, SBCU has been around for about seven years and trains dealers on bike fits using a system called Body Geometry Fit. BG Fit, as it's known, was developed by Dr. Andy Pruitt, founder of the Boulder Center for Sports Medicine and an expert in orthopedics and cycling mechanics. He created it as a step-by-step process that is "repeatable, and learnable, and delivers consistent results," says Sean Madsen, who has a degree in biomechanics and manages the program. The company's marketing tagline is "be one with your bike."

Specialized is certainly not alone in offering this sort of fitting, but it led the trend.

"Specialized Body Geometry Fit was the first scientifically based fit program to expose the greater community of cyclists to the benefits of bike fit," says Aaron Hersh, senior tech editor at Triathlete magazine. "Bike shops across the country have adopted serious fit programs since Specialized helped to popularize the notion that bike fit is key to enjoying cycling."

Aaron Post, a BG Fit teacher, notes that Pruitt was instrumental in getting some of these other programs launched. Pruitt helped a man named Ben Serotta start the Serotta International Cycling Institute. And Todd Carver, founder and lead fitter of Retul University, started out working with Pruitt.

Matt Smith, global manager of Retul University, the program offered at Race Pace in Columbia, notes that "most major bike brands have adopted some form of fit protocol to make sure that any rider — triathlete, mountain biker or recreational cyclist — is comfortable and happy on their bikes."

Stone isn't the only Specialized fitter in the area. BG Fits are also at Twenty20 Cycling and Lutherville Bikes, for example. There are 10 stores between D.C. and Philadelphia with a fitter who has gone through the "master's" level, as Stone did this spring.

But finding the right bike fitter is a process similar to finding the right yogi. And for some, Stone goes the extra mile.

Mike Yost of Bethesda is a convert. A lawyer with the Securities Exchange Commission, he's a marathon runner and started doing triathlons in 2006 at the age of 46. He said he's had "elaborate" and "expensive" bike fits in the past, but he started going to Stone about two to three years ago with his road bike and his race bike, and says now he won't go anywhere else. He says other fitters often "have preconceived notions of how you should fit on your bike — Mike looks at the rider and fits the bike to the rider." After his first fit with Stone, he qualified for the Ironman World Championship in Kona, Hawaii.

One with my bike

My first long ride on my new bike was a disaster. I felt out of control. Unsteady. My fingers and toes grew numb. I was sure I had made a terrible decision and wasted my money. I assumed I was the problem. I was too old to be riding a tri bike. But instead of giving up, I decided to think about the fit as an investment, and I called Stone.

One hour into my bike fitting, I wondered if I'd actually ever get on the bike. Stone had lots of questions. Why are you here? What sort of injuries have you had? Do you have any problems with knees? We went over my complete medical history.

From there, we moved into what felt like a physical therapy session. Stone had me do all sorts of tests: Stand on one leg and do a knee bend. Lie back on this table and do not resist as your leg is pressed back toward your head. At every point, Stone jotted down information, often measuring angles with what looked like a giant protractor.

And then finally we got to the bike, and the tests started anew, with more angle measuring and dropping of plumb balls.

Apparently, there were some good reasons I didn't like that first ride. My weight was back too far on the bike. The clip pedals on my shoes were in the wrong place. My arms were also in the wrong place. The seat was the wrong height. The tri bars — on the ends of which are the gear shifts — were way too far forward. Stone says that all my energy had gone into using my upper body to try to stay steady, and none of my strength was going into powering the bike. This was why I felt like I was about to keel over.

And so, after three hours with Stone, my relationship with my new bike changed. I still feared it a little bit, but I wasn't ready to kick it to the curb.

And now, I can't imagine I ever thought of giving up the bike. It makes me better, stronger, faster. Two weeks after my fitting, I shaved 15 minutes off my triathlon bike time. Now poor Fiona, my hybrid, sits gathering dust in the garage. Maybe someday I'll take it off to see the fitter, too.